Protozoa Flashcards
Describe the general features of the pyhlum Apicomplexa?
Mostly intracellular
Locomotion by gliding
Undergo sexual and asexual reproduction
Characteristic apical complex- involved in host cell invasion
What is the definitive host of toxoplasma gondii?
Cats
What are the three stages of Toxoplasma gondii and Neosporan caninum and briefly describe each
Tachyzoite- intracellular, rapidly dividing, crescent shaped
Bradyzoite- within bradyzoite cyst, neural or muscle tissue, slow growing, persistent
Oocyst- unsporulated oocyst passed in faeces, sporulated- two sporocysts, four sporozoites- 12um
Describe the life cycle of toxoplasma gondii
- Cats infected by ingesting bradyzoite cysts in tissues of prey
- Sexual cycle in small intestine- unsporulated oocysts shed in faeces
- Oocysts sporulate- contain two sporocysts each with four sporozoites, contaminate environment, food and water, can be ingested by any warm-blooded animal
- Infection in immunocompetent usually contained, vertical transmission during pregnancy
- In intermediate host- rodents birds- sporozoited released, cross gut wall, develop into tachyzoited, which replicate rapidly, differentiate into bradyzoite that form cysts
- Ingested by cats
What happens to toxoplasma gondii after ingestion by a cat?
Sexual reproduction
- Ingestion of prey containing bradyzoite cysts
- Cyst wall is digested in the stomach and intestines, liberating bradyzoites
- Bradyzoites invade epithelial cells of the intestine
- In the enterocytes bradyzoites divide by schizogony giving rise to merozoites
- Diffentiate into male and female gametocytes- microgamaetes and macrogametes
- Fertilisation gives rise to an unsporulated oocyst shed with cat faeces
- Sporulation occurs and generates sporocysts each with four sporozoites
How does toxoplasmosis affect cats and how is it controlled?
Vast majority are non-clinical, occasional systemic- immunosupressed
Control
Cats are the source of infection for sheep and humans
Control in cats is difficult- drugs not realistic, no vaccines
How does toxoplasmosis occur in humans?
Who is affected and what are the clinical signs?
How can someone become reinfected?
Transmission- tissue cysts in undercooked meat, ingesting oocysts contaminated food
Infection in immunocompetent usually contained- asymptomatic, flu-like symptoms, immunity
Bradyzoite cysts remain- can reactivate if person becomes immunosupressed
How does toxoplasmosis affect immunocompromised people?
What happens from vertical transmission in humans?
How is toxoplasmosis controlled in humans?
Immunocompromised- at serious risk of disease, primart infection or recrudesence of existing infection, severe life-threatening infection, transplant patients, toxoplasmic encephalitis in AIDs patients
Vertical transmission- infected prior to preg- foetus protected
Primary infection during pregnancy- miscarriage, hydrocephalus, convulsions, intercerebral calcification, retinochorioditis
Control- chemotherapy- pyrimethamine and sulphonamides, reduce risk of infection- oocysts in soul, cook meat
What is the definitive and intermediate host of neospora caninum?
Definitive- dog
Intermediate- dogs and cattle
How is neospora transmitted in dogs and cattle?
What are the disease signs?
Dog- ingestion of bradyzoited from bovine tissues- no disease shown- oocysts in faeces
Intermediate- dogs and cattle
Transplancental transmission- no oocysts in faeces
Disease
Dogs- neonatal paresis
Cattle- abortion
What are the clinical signs of neospora caninum in young dogs and older dogs?
Yound dogs- ataxia, hindlimb paralysis, loss of reflexes, ascending paralysis, dysphagia, hyperextension of hindlimb
Older dogs- CNS distubances, abnormal behaviour, vision defects, seizures, myocarditis, dermatitis, pancreatitis
How is neospora caninum diagnosed and controlled?
Diagnosis
- Clinical signs
- Serology by IFAT
- Creatine kinase elevation
- Muscle biopsy and tissue aspirates- PCR
- Oocysts rarely observed
Treatment
- Clindamycin
- Initiate treatment as soon as possible after clinical signs develop
- Prognosis variable
- Doesn’t stop vertical transmission
How many hosts are involved in sarcocystis spp life cycle?
Prey- asexualr reproduction and muscle cyst
Final predator- intestinal sexual reproduction and production of mature oocysts
Sheep- dog- S.capracanis, S. hiricanis
Cattle- cat- S. hirsuta
How is sarcocystis spp transmitted?
What happens if sarcocysts are found?
What happens if cattle are infected in second or third trimester of pregnancy?
How does it affect dogs and cats?
Transmitted by sporolated oocysts in predator species faeces- eaten by prey species- sprocyst- eaten by predator
Meat condemed if sporocysts found
Cattle abort in third trimester infection- nothing in second AHHHH
Dogs and cats- no clinical signs, mild diarrhoea
What species does cystoisospora spp affect?
How many hosts are involved in its life-cycle?
How is the parasite transmitted?
How is the disease diagnosed and controlled?
Several species- dogs and cats
Direct life cycle- 1 host, can have intermediate
Transmitted by oocysts passed in faeces
Diagnosis- history and clinical signs (diarrhoea in puppies and kittens), oocysts sometimes differentiated on size
Control- good sanitation and treat with sulphonamides
